The present invention relates essentially to an improved machine for insolating photopolymer plates for flexographic printing.
There has already been proposed machines suitable for carrying out the insolation of photopolymer plates with the assistance of a source of ultraviolet light.
In a general manner these machines comprise a frame above which is arranged at least one bank or row of ultraviolet lamps.
Upon the upper part of the frame underneath the bank of ultraviolet lamps one places a photopolymer plate which is insolated by the lamps through a negative film placed on the plate. The film-plate assembly is held under vacuum on the upper portion of the frame of the machine with the assistance of a transparent membrane.
It has now been found that the energy of the ultraviolet lamps heats the space defined by the transparent membrane and the upper portion of the frame of the machine, i.e. the space containing the negative film and the flexographic plate.
It results therefrom that in spite of the vacuum provided in that space, the latter forms a gas pocket which results in the separation or disconnection of the flexographic plate from the negative film.
One therefore is subjected to bad insolation conditions so that one eventually obtains a printing plate which is fuzzy.
More specifically after the insolation of the plate under the bad conditions stated hereinabove and after washing of this insolated plate with a solvent, it appears that there is a bad definition or resolution of the relief of the plate produced by the ultraviolet light which either travels through the transparent zones of the negative film or is stopped by the opaque zones of this film, so that the printing provided by this plate after inking thereof will be fuzzy.
Therefore the object of the present invention is to remedy these inconveniences by providing an improved machine owing to which the flexographic plate to be insolated will not undergo any disturbance or trouble due to the heat of the ultraviolet light lamps.